JPH04314716A - Production of urethane resin - Google Patents

Abstract

PURPOSE:To produce a urethane resin in which a dye or pigment disperses well and which is useful for a toner for electrophotography by reacting a polyol with a specified ant. of an isocyanate compd. under specified conditions of reaction temp. and cooling rate after the reaction. CONSTITUTION:A polyol (e.g. a polyester polyol obtd. by reacting propoxylated bisphenol A, 1,3-butylene glycol, trimethylolpropane, and isophthalic acid) and an isocyanate compd. (e.g. tolylene diisocyanate) in a molar ratio of NCO groups to OH groups of 1.0-1.3 are reacted under such conditions that the reaction temp. T( deg.C) and the cooling rate after the reaction -(dT/Dt)( deg.C/min) satisfy the relation: -(dT/dt)<=0.314XT-16.7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a urethane resin, and more particularly to a method for producing a urethane resin for use in electrophotographic toners having good dye and pigment dispersibility.

0002

[Prior Art] Electrophotography uses a photoconductive substance to form an electrical latent image on a photoreceptor by various means, and then develops this latent image with toner, and if necessary, prints it on paper, etc. After the image is transferred onto an image support, it is fixed using a heating roll or the like to obtain an image. Various toner resins have been studied for use here, but polyurethane resins, when melted, have good dispersion of toner additives such as carbon black and good wetting to transfer paper, and have excellent fixing properties. Currently, it is widely used as a toner for heating roll fixing because it has the advantage that it has excellent properties.

Furthermore, in recent years, there has been an increasing demand for simplifying the developing mechanism, reducing its weight, and emphasizing image clarity, and a one-component developing method that does not use so-called carrier particles to charge the toner has been developed. It is being put into practical use.

0004

[Problems to be Solved by the Invention] In electrophotography, it is essential to provide clear images in a stable manner at all times from the standpoint of transmitting information. For this purpose, it is necessary to improve the dispersion of the dye and/or pigment contained in the toner. Regarding the dispersibility of dyes and pigments, there is a method of increasing the viscosity and gel fraction of the binder resin in the kneading process during toner production, and generating high mechanical shearing force in the kneading equipment to improve the dispersibility of dyes and pigments. .

[0005] If the dispersibility of the dye and pigment is poor, the charge amount distribution of the toner particles becomes uneven, and in the region of high charge amount, the toner with an abnormally high dye and pigment content is strongly charged on the developing sleeve. adhere to. For this reason, toner particles accumulate without being developed and are eventually fused onto the sleeve by the frictional pressure of the charging blade, resulting in so-called sleeve contamination. Due to this sleeve contamination, the toner conveyance and charge imparting properties of the developing sleeve are significantly reduced, and the toner conveyed to the contaminated area is not sufficiently charged, resulting in a decrease in image density and print quality. It becomes extremely bad.

One way to improve the dispersibility of dyes and pigments is to increase the viscosity of the binder resin. However, if the viscosity of the binder resin is high, the thermal fluidity of the toner deteriorates, and the adhesion of the toner particles to the paper to be fixed becomes incomplete during hot roll fixing, resulting in toner peeling off, making it difficult to achieve good print quality. is difficult.

[0007]Also, there is a method of improving the dispersibility of dyes and pigments by increasing the gel fraction of the binder resin, but among the styrene-based, polyester-based, and urethane-based resins that are generally used as binder resins, urethane-based resins are particularly used. However, products with a high gel fraction have high viscosity, and if dispersibility is improved, thermal fluidity will deteriorate. There is an increasing need to develop urethane resins with good thermal fluidity.

[0008]

[Means for Solving the Problems] The present inventors have conducted extensive studies to develop a urethane resin with excellent properties for use in toners that has sufficient performance to satisfy these demands. We discovered an excellent method for producing urethane resin that was not possible with technology, and completed the present invention.

That is, the present invention provides polyol (A) and (A
) in the production of a urethane resin (C) with a glass transition temperature of 40 to 80°C obtained by reacting 1.0 to 1.3 molar equivalents of isocyanate compound (B) per 1 molar equivalent of hydroxyl groups in the urethanization reaction temperature. The cooling rate after the T and urethanization reaction -(dT/dt) is -(dT/dt)≦
This is a method for producing a urethane resin characterized in that it is within the range shown by 0.314 x T-16.7. Here, T
The unit of is (℃), and the unit of dT/dt is (℃/mi
n. ).

The urethane resin referred to in the present invention is obtained by reacting a polyol (A) and an isocyanate compound (B), and the polyol (A) may include polyester polyol, polyether polyol, polyacrylic polyol, or has a mixture of these.

[0011] The polyester polyol mentioned here is obtained by polycondensation of a polyhydric carboxylic acid and a polyhydric alcohol, and the polyhydric carboxylic acid as a raw material is
Aliphatic dibasic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and hexahydrophthalic anhydride, and aromatic dibasic acids such as phthalic anhydride, phthalic acid, terephthalic acid, and isophthalic acid. and lower alkyl esters thereof, and aromatic tribasic acids such as trimellitic acid.

[0012] Examples of polyhydric alcohols include ethylene glycol, 1,2-propylene glycol,
1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-
Diols such as hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, hydrogenated bisphenol A, bisphenol A propylene oxide adduct, and triols such as glycerin, trimethylolpropane, trimethylolethane, etc.
Among these, bisphenol A propylene oxide adduct is particularly preferred.

[0013] Polyether polyols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A ethylene oxide adduct, bisphenol A
These include propylene oxide adducts.

Polyacrylic polyol is a homopolymer of a vinyl monomer having a hydroxyl group in the molecule or a copolymer with other vinyl monomers, and is a vinyl monomer having two or more hydroxyl groups in the molecule. It is a polymer. Examples of vinyl monomers having a hydroxyl group in the molecule include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and other vinyl monomers include is ethylene, propylene, 1-butene, 2-butene, butadiene, acrylonitrile, vinyl chloride, vinyl bromide, styrene, α-methylstyrene, methyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl Examples include methacrylate, isobutyl acrylate, 2-ethylhexyl methacrylate, acrylic acid, and methacrylic acid.

[0015] Furthermore, the isocyanate compound (B) of the present invention
Examples of the diisocyanate include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate.

The isocyanate compound (B) is usually used in an amount of 1.0 to 1.3 molar equivalents, particularly 1.05 to 1.1 molar equivalents per 1 molar equivalent of hydroxyl groups in the polyol (A).
5 molar equivalents are preferred. Isocyanate compound is 1.0
If the molar equivalent is less than 0, the dispersibility of dyes and pigments decreases when used as a binder for toner, which is undesirable.
If the molar equivalent is exceeded, the fixing properties of the toner will deteriorate, which is undesirable.

The urethane resin (C) can be obtained, for example, by the following method. That is, 1.0 to 1 mole of the isocyanate compound (B) is added to 1 mole of the hydroxyl group of the polyol (A).
Using 1.3 mol, the reaction temperature T is 60 to 190°C, and it is charged all at once, in parts, or continuously into a batch type kneader, single-screw kneader, twin-screw kneader, static mixer, etc., and the reaction temperature is set at T. After reacting at T for several minutes to several hours, it is cooled to a solid resin using a heat exchanger type cooler, mixer type cooler, cold air conveyor cooler, chill roll type cooler, belt type cooler, etc. It can be obtained by

A major feature of the urethane resin manufacturing method of the present invention is the cooling rate when the resin reacted at the reaction temperature T is cooled to solidify. That is, the reaction temperature is T,
-(dT/dt) when the cooling rate is -(dT/dt)
)≦0.314×T-16.7 When urethane resin is produced with a reaction temperature and cooling rate that satisfy the relationship, the viscosity does not increase significantly despite the increase in the gel fraction of the urethane resin produced. As a result, the dye and pigment have good dispersibility and fixability, which is preferable. If the reaction and cooling are carried out outside the range of the above formula, the viscosity will increase significantly even though the gel fraction does not increase, resulting in poor dye and pigment dispersibility and poor fixability, which is not preferred.

When the urethane resin of the present invention is used as an electrophotographic toner composition, the above urethane resin (C)
A suitable coloring agent, a charge control agent, and further additives are added as necessary to form a composition.

Specific examples of colorants, charge control agents, additives, etc. that can be used in this composition are as follows.

Suitable colorants include, for example, carbon black, aniline blue, alcohol blue, chrome yellow, ultramarine blue, quinoline yellow methylene blue, phthalocyanine blue, malachite green, rose bengal, magnetite and the like.

[0022] Furthermore, as the charge control agent, all conventionally known charge control agents can be blended. Examples include nigrosine, triphenylmethane dyes, and chromium complexes of 3,5-di-t-butylsalicylic acid.

As additives, all conventionally known additives can be used, such as colloidal silica, zinc stearate, low molecular weight polypropylene, stearamide, methylene bisstearamide, and magnetic powder.

Furthermore, for the production of toner, the above-mentioned resin and other compounds are premixed using a Henschel mixer or the like, and then melt-kneaded using a kneader or the like at a temperature of 100 to 180°C.
The obtained lumps can be crushed and classified to provide particles with a particle size of 5 to 15 μm for electrophotographic toner.

[0025]

[Examples] Next, the present invention will be specifically explained with reference to Examples. Note that hereinafter "parts" represent parts by weight unless otherwise specified. Examples 1 to 40 Production examples of urethane resin (C) are shown below. KB300K
(Propoxylated bisphenol A, manufactured by Mitsui Toatsu Chemical Co., Ltd.) 0.8 mol, 1,3-butylene glycol 0.1
Hydroxyl value: 42 mgKOH/g, consisting of 6 mol, trimethylolpropane 0.04 mol, and isophthalic acid 0.9 mol
The polyester polyol (A) was urethane modified using a twin screw extruder (TEX-30 manufactured by Japan Steel Works, Ltd.). As for the extrusion conditions, the extruder cylinder temperature was set so that the urethanization reaction temperature was as shown in Table 1, and the screw rotation speed was adjusted so that the average residence time of the resin was 20 minutes. Urethane modification is carried out by continuously feeding polyol (A) into an extruder at a predetermined rate using a metering pump, melting and kneading it, and then vacuuming the volatile content in the resin through the first vent port provided in the extruder. and then from the second vent port the ratio of hydroxyl groups to isocyanate groups (NCO/OH) shown in Table 1.
A predetermined amount of the isocyanate compound (tolylene diisocyanate) (B) was continuously supplied using a metering pump to cause a reaction. Obtained urethane resin (C)
were cooled at the cooling rates shown in Table 1, Table 2, Table 3 and Table 4 (Table-1), finally cooled to 20°C, and then crushed.

Example 41 Hydroxyl value 40mgKOH consisting of styrene, n-butyl acrylate, and 2-hydroxyethyl methacrylate
The urethane resin (
When C) was produced, the gel fraction of this urethane resin (C) was 15.2%.

[0027] Furthermore, this urethane resin (C) was applied in Application Example 1.
When the performance as an electrophotographic toner was investigated in the same manner as in ~40, the fixing residual rate was 89%, and the sleeve stainability was ○.
The durable image density was 1.3.

Application Example Urethane resin (C) 1 obtained in Production Examples 1 to 40
00 parts by weight, 6 parts by weight of carbon black MA-100 (manufactured by Mitsubishi Kasei Co., Ltd.), 2 parts by weight of Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.) as a charge control agent, and polypropylene wax Viscole 55OP (manufactured by Sanyo Chemical Industries, Ltd.). After dispersing and mixing 2 parts by weight of (manufactured by Ikegai Tekko Co., Ltd.) in a Henschel mixer, the mixture was mixed at 160°C in a twin-screw kneader PCM30 (manufactured by Ikegai Tekko Co., Ltd.).
The mixture was melted and kneaded to obtain a bulk toner composition.

After coarsely pulverizing this composition with a hammer mill, a jet pulverizer (IDS2 manufactured by Nippon Pneumatic Co., Ltd.) was used.
finely pulverized using a mold) and then air-classified to an average particle size of 10 μm.
Toner particles of m (3% by weight of 5 μm or less, 2% by weight of 20% or more) were obtained. Table 4 shows the properties of the obtained toner particles.
It was shown to. 100 parts by weight of this toner was mixed with 1 part by weight of hydrophobic silica Aerosil R970 (manufactured by Nippon Aerosil Co., Ltd.) to prepare a one-component developer.

A copying test was conducted using a commercially available non-magnetic one-component type laser beam printer (LP3000 manufactured by Seiko Epson Corporation) at a room temperature of 25° C. and a relative humidity of 50% while changing the temperature of the heat roller. Table 1 shows the evaluation results of the fixing temperature range, developing sleeve contamination during printing, and image density stability.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4] As can be seen from the results in Table 1, by using the toner obtained according to the present invention, it was possible to obtain good images with excellent fixing properties and excellent long-term image density stability.

[0035] Notes in the table are as follows. 1) Weight fraction of the resin part insoluble in ethyl acetate relative to the whole 2) A toner layer was placed on the image of a solid black part of 2 cm x 2 cm using a Gakushin friction fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.). Minimum heat fixing roll surface temperature required for the weight residual rate of the toner layer to exceed 80% after being rubbed 50 times with a sand eraser under a load of 125 g/cm2 3) The state of formation of the thin toner layer on the developing sleeve. The degree of damage was determined visually. ○: A uniform thin toner layer is formed. Δ: There is a thin toner layer missing at both ends. x: There is a lack of a thin toner layer throughout. 4) The degree of blackness of solid black areas in the image after 10,000 copies was determined using a Beckman reflection densitometer.

Claims (1)

[Claims] [Claim 1] In the production of a urethane resin (C) obtained by reacting a polyol (A) with an isocyanate compound (B) in an amount of 1.0 to 1.3 molar equivalents per 1 molar equivalent of hydroxyl groups in (A). A urethane resin characterized in that the conversion reaction temperature T and the cooling rate after the urethanization reaction -(dT/dt) are within the range expressed by -(dT/dt)≦0.314×T-16.7. manufacturing method.